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building on mips
by Max Suraev 29 Apr '09

29 Apr '09

Hello. Could you please help me with bug #2972: https://svn.boost.org/trac/boost/ticket/2972 I'm trying to compile boost trunk on mips with cmake but got error described in this ticket. Have someone tried to cross-compile boost for mips? Any ideas will be welcomed - I'm afraid that I'm missing something obvious here. best regards, Max.

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[GIL] How can I copy a subimage_view to a view?
by blp330 29 Apr '09

29 Apr '09

Hi, I wrapped boost::gil::rgb8_image_t::view_t as a simple class Image: class Image { public: // ... some methods here. private: boost::gil::rgb8_image_t::view_t view; }; And I have a method Crop, which is crop image to other image object, like this: void Image::Crop(int x, int y, int width, int height, Image& out) const { boost::gil::rgb8_image_t s(width, height); boost::gil::copy_pixels( boost::gil::subimage_view(view, x, y, width, height), boost::gil::view(s)); out.view = boost::gil::view(s); } I will get error after I run this code... But I can't understand what's wrong. So, how can I implement this? Thank you very much. -- View this message in context: http://www.nabble.com/-GIL--How-can-I-copy-a-subimage_view-to-a-view--tp232… Sent from the Boost - Users mailing list archive at Nabble.com.

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Another BGL question
by Lindley M French 28 Apr '09

28 Apr '09

Here's my problem. I've got a very large graph (say a few thousand nodes). This graph is planar, although that doesn't really affect much. Small clusters of vertices are grouped into "regions". The edges within a region are marked as "on", and those between regions are marked as "off". I need to be able to pull all vertices from a region and some or all of its neighboring regions, as well as all induced edges, into a local graph that I do work on. At first I thought of using the subgraph function together with copy_graph, but the subgraph interface is pretty unintuitive, so I'm avoiding it for now. I have a mechanism to iterate over all the vertices in a region, but not the edges. How can I get an iterator to the edges around a given vertex or set of vertices? adjacency_iterator isn't the right tool. Is there an exhaustive list of all iterators available in BGL somewhere?

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[BOOST THREAD] Threads Spawning Unexpectedly
by Terrimane Pritchett 28 Apr '09

28 Apr '09

Hello, I have taken interest in using Boost Threads in my project. I have a strange issue that I am trying to debug. I spawn N boost::thread instances because I know exactly how many I need. My program crashes after a time on a boost::bad_lexical_cast exception. I have placed a wrapper around boost::lexical_cast which uses a boost::recursive_mutex and boost::lock_guard combination to prevent multiple threads from calling boost::lexical_cast at the same time. Still, my project invariably chokes on boost::bad_lexical_cast being thrown when I can verify the cast should work i.e. everything works as expected in my single threaded implementation. My real cause for alarm is this....when I act to debug my project I always discover there are more active boost::thread instances than I have explicitly created. I only create boost::thread instances in one location. I have perused the documentation but as of yet cannot find an explanation for this behavior. My assumption is that unless I explicitly instantiate a boost::thread it should not exist. However, I want to ask if this is indeed the case? If not, how so and what is the rationale behind this behavior? Here is what my code more or less looks like - this is all I do with boost::threads currently - how are more than N boost::threads spawning where N is the number of elements in an arbitrary stl container which itself is not allowed to change in size? typedef boost::shared_ptr<boost::thread> THREADHANDLE; typedef std::vector<THREADHANDLE> THREADHANDLECONTAINER; THREADHANDLECONTAINER workerThreads; workerThreads.reserve(some_container.size()); ... workerThreads.push_back( THREADHANDLE(new THREADHANDLE::element_type( Callable, arg1, boost::ref(arg2)); ... BOOST_FOREACH(const THREADHANDLE &workerThread,workerThreads) { workerThread->join(); }//end loop ------------------------------------------ Here is my attempt at using boost::lexical_cast in a generic thread safe manner. I am expecting exactly one thread my call boost::lexical_cast at a time with this wrapper yet my application blows up solely on boost::bad_lexical_cast whenever I introduce Boost Threads. Am I missing the elephant in the room somehow? //LexicalCaster.h #include <boost/thread.hpp> struct LexicalCaster { template<typename TargetType,typename SourceType> inline static TargetType LexicalCast(const SourceType &source); private: static boost::recursive_mutex& GetMutex(); static int& GetCount(); }; //LexicalCaster.cpp #include "LexicalCast.h" boost::recursive_mutex _mtx; int count(0); //here for debugging purposes boost::recursive_mutex& LexicalCaster::GetMutex() { return _mtx; } int& LexicalCaster::GetCount() { return count; } //LexicalCaster.inl #include <boost/lexical_cast.hpp> template<typename TargetType,typename SourceType> TargetType LexicalCaster::LexicalCast(const SourceType &source) { boost::lock_guard<boost::recursive_mutex> guardian(LexicalCaster::GetMutex()); std::cerr<<"Count: "<<LexicalCaster::GetCount()++<<std::endl; //the count will display sequentially if only //one thread of execution has access at a time return boost::lexical_cast<TargetType>(source);

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Re: [Boost-users] Serialization problem with DLL & EXE
by Andrei Popa 28 Apr '09

28 Apr '09

Hi Robert, With a class derived from DbObject and defined/implemented in my EXE (that use the DLL) I got archive_exception::unregistered_class. I tried to register it or to export it, but I could not make it work. *** So you put BOOST_CLASS_EXPORT(DbObject) in to a *.cpp file which is compiled as part of the exe? Yes, I do. Any Ideas? I use Version 1.38 of the library & VC8(2005). When I use BOOST_CLASS_TYPE_INFO(as in test_no_rtti.cpp sample ) for my EXE resident class, the ::get_key is never called. // get the eti record for the exported type "polymorphic_derived2" boost::serialization::extended_type_info const * const d2_eti = boost::serialization::extended_type_info::find( "polymorphic_derived2" ); works too before I start to serialize the collection. *** is this an attempt the issure raised above or is this a separate question. No separate question at all, this is the way I tried figure out if my class is really (and correctly) registered. Is this a correct way to test? How can I debug what's wrong? Thanks Andrei. _________________________________________________________________ News, entertainment and everything you care about at Live.com. Get it now! http://www.live.com/getstarted.aspx

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Serialization problem with DLL & EXE
by Andrei Popa 28 Apr '09

28 Apr '09

Hi there, I have a dll that contain an abstract base class called DbObject and a DbDatabase class that contains a collection of shared_ptr<DbObject> . It dose work as long all derived classes are defined in the same dll. With a class derived from DbObject and defined/implemented in my EXE (that use the DLL) I got archive_exception::unregistered_class. I tried to register it or to export it, but I could not make it work. Any Ideas? I use Version 1.38 of the library & VC8(2005). When I use BOOST_CLASS_TYPE_INFO(as in test_no_rtti.cpp sample ) for my EXE resident class, the ::get_key is never called. // get the eti record for the exported type "polymorphic_derived2" boost::serialization::extended_type_info const * const d2_eti = boost::serialization::extended_type_info::find( "polymorphic_derived2" ); works too before I start to serialize the collection. Thanks, Andrei _________________________________________________________________ Show them the way! Add maps and directions to your party invites. http://www.microsoft.com/windows/windowslive/products/events.aspx

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po::program_options
by Zarkvon 28 Apr '09

28 Apr '09

Hello, During using library 'program_options' we noticed some issues. The first one is that class 'duplicate_option_error' never uses. /** Class thrown when duplicate option description is found. */ class BOOST_PROGRAM_OPTIONS_DECL duplicate_option_error : public error { public: duplicate_option_error(const std::string& what) : error(what) {} }; And the second one which is critical for us. Is that all errors are forming as one sentence in ENGLISH. And it's an issue to get which exception exactly occured to form your own message in your desired language. For instance class - validation_error. I guess it's really hard and inconvinient to get what message should be thrown. So, what will you advise to do to make this library more "international", so all exception messages are put out in any language which programmer wants.

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Boost Graph Library mysterious compile errors
by Lindley M French 28 Apr '09

28 Apr '09

Follow-up: It appears to be related to the edge_weight property. Judging by the documentation I was under the impression that this was a default property that all edges would have. Is this not the case? How would I add it? I already tried putting a "double edge_weight" field in my EdgeProperties struct, didn't help.

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[graph] ColorMap
by liquid 28 Apr '09

28 Apr '09

Please, help me to declare correctly the ColorMap as the 3-rd parameter of depth_first_search function. Documentation does not explain it clearly. Regards liquid

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Boost & Continuous Integration
by Robert Dailey 28 Apr '09

28 Apr '09

Hey guys, One of the requirements for a continuous integration process is that the build for a specific target be quick. Something under 10 minutes is ideal. I find that when not using precompiled headers, boost can significantly impact the compilation time of the project. I've experienced 20 minute compiles when using boost fairly extensively throughout the code base. So far I only see two obvious solutions to this problem. First, use precompiled headers. I really don't want to do this because it causes issues with include dependencies and makes the code not reusable as a result. The second option is to beef up the machines doing the compiles, however this can have diminishing returns. I am sure that a lot of people in the community have had this specific issue with Boost's compile times, as well as in many other areas. What would you guys recommend? Is there any other solution beyond the obvious? Thanks for your time.

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Boost Graph Library mysterious compile errors
by Lindley M French 28 Apr '09

28 Apr '09

I'm getting some mysterious compile errors relating to boost::detail::error_property_not_found. Truely massive errors, well too large to get any useful information out of.....ah, templates. I eventually figured out that these sorts of errors are usually related to BGL algorithm calls which can't find the properties they need. (Wow, thanks for pointing me right at the source, template error...) Well, the only algorithms I'm calling right now are connected_component and kruskal_minimum_spanning_tree. One such instance occurs with a particular connected_component call: typedef boost::adjacency_list< boost::listS, boost::vecS, boost::undirectedS, RegionProperties, EdgeProperties> Graph; template <typename Graph> struct edge_on { edge_on(): m_G(NULL) { } edge_on(const Graph &G) : m_G(&G) { } template <typename Edge> bool operator()(const Edge& e) const { return (*m_G)[e].on; } const Graph *m_G; }; ... //function arg ....(Graph &G,... filtered_graph<Graph, edge_on<Graph> > G_on_edges(G, edge_on<Graph>(G)); std::vector<int> component(num_vertices(G_on_edges)); int num_comps = connected_components(G_on_edges, &component[0]); Do you see anything wrong there? The kruskel call (which is producing more such errors) is Graph comp_G; .... vector<Edge> mstedges; mstedges.reserve(num_vertices(comp_G)); kruskal_minimum_spanning_tree(comp_G,std::back_inserter(mstedges)); I really have no idea what might be wrong here.

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filtered_graph question
by Lindley M French 28 Apr '09

28 Apr '09

If I construct a filtered_graph on some underlying graph, and then (either through it or via another interface) modify the underlying graph to change which edges make it through the filter....when is this change reflected? Do I have to construct another filtered_graph? Or is it immediate? Will it invalidate iterators or anything like that? I'm just trying to get my head around the conceptual workings here.

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Use of Boost [threadpool] library w/ Windows Service Process
by Art Beall 27 Apr '09

27 Apr '09

Hello, Our application was in need of a thread pool for processing socket messages. During implementation and testing we were using the [threadpool] library along with Boost v36. We are using Visual Studio 2003 for building our application. Our target systems are running Windows Server 2003 or Windows XP Pro. The windows console version of our application runs great. No problems with thread pooling. However, once we use it inside a windows service, the application fails to load. No code is actually executed. After doing a lot of research into the problem, I narrowed it down to the inclusion of the threadpool object into the code. One caveat with using the application as a windows service, the main project is compiled /clr (managed code). However, I've placed all code that refers to boost in a separate library compiled as unmanaged code. This library is linked with both the console application (working), and the service application (won't load). Does anyone have any ideas what would cause this ? Thanks! Art Beall

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[Fwd: io_service::strand - order of execution guarantees]
by Chris Hite 27 Apr '09

27 Apr '09

Can someone give me a guarantee about the order in which operations dispatched./posted to a strand are executed? Obviously if two different threads call post() or dispatch(), there is a race condition. However if one thread calls dispatch() twice, can it be sure that the first handler executes before the second? What happens if post() and dispatch() are mixed? Looking at the library it appears that a posted handler causes any subsequent dispatches to act exactly as posts. It appears as though a strong guarantee is being made: All handlers posted or dispatched will execute in order. If such a useful guarantee is required internally by asio, it should be made public and be documented. Christopher Hite RTS Realtime Systems Software GmbH, Rembrandtstrasse 13, D-60596 Frankfurt am Main T: +49.69.61009.0 / F: +49.69.61009.181 Sitz: Frankfurt am Main - HRB 84467 Amtsgericht Frankfurt am Main Geschäftsführer: Steffen Gemuenden, Igor Sluga www.rtsgroup.net This email and any attachments are for the exclusive and confidential use of the intended recipient. If you are not the intended recipient, or an employee or agent responsible for delivering this message to the intended recipient, please do not read, distribute or take action in reliance upon this message. If you have received this in error, please notify me immediately by return email and promptly delete this message and its attachments from your computer system.

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[lambda] Return types in lambda expressions
by Michael Crawford 27 Apr '09

27 Apr '09

I'm trying to use bind and lambda to create a functor that can receive an event generated by my GUI library, and dispatch an appropriate event into a boost::statechart::state_machine. The GUI library requires the functor to have the signature bool (const CEGUI::EventArgs&). An example of what works: template<typename EventType> bool GuiEvent(const CEGUI::EventArgs&, GameStateMachine& gsm) { gsm.process_event(EventType( )); return true; } //usage: GameStateMachine sm; ... boost::bind(&GuiEvent<EventExitGame>, _1, boost::ref(sm)); But is it possible to use lambda to eliminate the need for the function? It looks like I would use something along the lines of boost::bind<bool>(boost::ref(sm).process_event(EventExitGame( )) /*somehow return true here*/, _1); I'm just not quite seeing how I would get the lambda expression to return true there. Cheers.

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Re: [Boost-users] undefined reference to `__sync_fetch_and_add_4'
by Birju Prajapati 27 Apr '09

27 Apr '09

I figured it out. It was an obscure, seemingly undocumented option to bjam: instruction-set=i686 i.e bjam architecture=x86 address-model=32 instruction-set=i686 --stagedir=stage32 --with-filesystem --with-thread --with-signals --with-serialization --with-system --with-program_options --with-date_time stage Could anyone point me to where I would have found that without grepping gcc.jam? From: Birju Prajapati Sent: 24 April 2009 13:12 To: boost-users(a)lists.boost.org Subject: undefined reference to `__sync_fetch_and_add_4' Hi, I built boost 1.38 as so: bjam architecture=x86 address-model=32 --stagedir=stage32 --with-filesystem --with-thread --with-signals --with-serialization --with-system --with-program_options --with-date_time stage Copied the files over to /usr/local/lib32: sudo cp stage32/lib/* /usr/local/lib32/ Compiled object files, eg: g++ -m32 -c -g -D_LINUX -I. -I/opt/sts_vendor/onix-eurex/include -I/usr/local/include/boost-1_38 -MMD -MP -MF build/Debug/GNU-Linux-x86/reference/ReferenceData.o.d -o build/Debug/GNU-Linux-x86/reference/ReferenceData.o reference/ReferenceData.cpp Then linking does not work: g++ -m32 -o dist/Debug/GNU-Linux-x86/spreadx build/Debug/GNU-Linux-x86/multicast/MulticastChannel.o build/Debug/GNU-Linux-x86/reference/ReferenceData.o build/Debug/GNU-Linux-x86/reference/Strategy.o build/Debug/GNU-Linux-x86/executor/MessageExecutor.o build/Debug/GNU-Linux-x86/multicast/MulticastSelector.o build/Debug/GNU-Linux-x86/fast/FIXStreamSubscriber.o build/Debug/GNU-Linux-x86/reference/Product.o build/Debug/GNU-Linux-x86/spreadx.o build/Debug/GNU-Linux-x86/fast/FIXMessage.o build/Debug/GNU-Linux-x86/multicast/Message.o build/Debug/GNU-Linux-x86/fast/FastDecoder.o build/Debug/GNU-Linux-x86/reference/Outright.o -L/opt/sts_vendor/onix-eurex/lib -L/usr/tibco/tibrv/lib -L/usr/local/lib32 -lffCppFixEngine -lACE -lcrypto -lboost_serialization-gcc43-mt -lboost_system-gcc43-mt -lboost_thread-gcc43-mt /usr/local/lib32/libboost_serialization-gcc43-mt.so: undefined reference to `__sync_fetch_and_add_4' I've tried #define BOOST_SP_USE_PTHREADS in user.hpp, I've tried -march=i486, but neither works. What gives? My platform details: birju@xx:~$ g++ --version g++ (Ubuntu 4.3.2-1ubuntu12) 4.3.2 Copyright (C) 2008 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. birju@xx:~$ uname -a Linux xx 2.6.27-11-generic #1 SMP Wed Apr 1 20:53:41 UTC 2009 x86_64 GNU/Linux birju@xx:~$ Cheers, Birju Schneider Trading 4th Floor, 25 Copthall Avenue London EC2R 7BP -------------------------------------------------------- Message from: Birju.Prajapati(a)schneidertrading.com Message to: boost-users(a)lists.boost.org Attached files: 0 This e-mail and any files transmitted with it are confidential, may be legally privileged, and are for the sole use of the intended recipient. Copyright in this e-mail and any accompanying document created by us is owned by us. If you are not the intended recipient of this e-mail or any part of it please telephone our IT Department at the number shown above or by e-mail at info(a)schneidertrading.com. You should not use or disclose to any other person the contents of this e-mail or its attachments (if any), nor take copies. This e-mail is not a representation or warranty and is not intended nor should it be taken to create any legal relations, contractual or otherwise. Schneider Trading Associates Ltd (Registration No. 3692131) is incorporated in England and Wales and the registered office is at 25 Copthall Avenue, London EC2R 7BP. The company is authorised and regulated by the Financial Services Authority

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[Statechart] Passing reference to create_processor()
by Hawkes Steve-FSH016 27 Apr '09

27 Apr '09

The Boost reference states that boost::ref can be used to pass an argument to statechart::fifo_scheduler::create_processor by reference instead of by value. I haven't been able to get this to work if the argument type derives from boost::noncopyable. It appears that the create_processor implementation instantiates code that attempts to copy the argument. Here's an example. Note that this compiles and runs sucessfully if Object does not derive from boost::noncopyable. Thanks, Steve Hawkes ---- #include <boost/statechart/asynchronous_state_machine.hpp> #include <boost/statechart/fifo_scheduler.hpp> #include <boost/statechart/simple_state.hpp> #include <boost/noncopyable.hpp> #include <boost/ref.hpp> #include <iostream> class Object : public boost::noncopyable { }; struct Initial; struct Test : boost::statechart::asynchronous_state_machine<Test, Initial> { public: Test(my_context ctx, Object& arg1) : my_base(ctx) { } }; struct Initial : boost::statechart::simple_state<Initial, Test> { }; int main() { Object value; boost::statechart::fifo_scheduler<> scheduler; const boost::statechart::fifo_scheduler<>::processor_handle processor1 = scheduler.create_processor <Test, Object&> (boost::ref(value)); return (0); } ---- Here's the compiler error: ---- g++ -Wall -lboost_system-mt -lboost_thread-mt -o test test.cc /usr/include/boost/noncopyable.hpp: In copy constructor 'Object::Object(const Object&)': test.cc:9: instantiated from 'typename boost::statechart::processor_container<boost::statechart::fifo_scheduler <FifoWorker, Allocator>, typename FifoWorker::work_item, Allocator>::processor_handle boost::statechart::fifo_scheduler<FifoWorker, Allocator>::create_processor(Arg1) [with Processor = Test, Arg1 = Object&, FifoWorker = boost::statechart::fifo_worker<std::allocator<void> >, Allocator = std::allocator<void>]' test.cc:36: instantiated from here /usr/include/boost/noncopyable.hpp:27: error: 'boost::noncopyable_::noncopyable::noncopyable(const boost::noncopyable_::noncopyable&)' is private test.cc:9: error: within this context /usr/include/boost/statechart/fifo_scheduler.hpp: In member function 'typename boost::statechart::processor_container<boost::statechart::fifo_scheduler <FifoWorker, Allocator>, typename FifoWorker::work_item, Allocator>::processor_handle boost::statechart::fifo_scheduler<FifoWorker, Allocator>::create_processor(Arg1) [with Processor = Test, Arg1 = Object&, FifoWorker = boost::statechart::fifo_worker<std::allocator<void> >, Allocator = std::allocator<void>]': /usr/include/boost/statechart/fifo_scheduler.hpp:63: note: synthesized method 'Object::Object(const Object&)' first required here /usr/include/boost/statechart/fifo_scheduler.hpp:63: error: initializing argument 3 of 'WorkItem boost::statechart::processor_container<Scheduler, WorkItem, Allocator>::create_processor(boost::weak_ptr<std::auto_ptr<boost::statec hart::event_processor<Scheduler> > >&, Scheduler&, Arg1) [with Processor = Test, Arg1 = Object, Scheduler = boost::statechart::fifo_scheduler<boost::statechart::fifo_worker<std::al locator<void> >, std::allocator<void> >, WorkItem = boost::function0<void>, Allocator = std::allocator<void>]'

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[Review Results] Range.Ex library accepted into boost
by Thorsten Ottosen 27 Apr '09

27 Apr '09

Dear all, It is my pleasure that Neil Groves' RangeEx library has been accepted into boost. Congratulations Neil! There are quite a number of minor issues that need to be resolved before the library is release ready, see below for a summary. Review statistics ----------------- Full Reviews: 8. Discussion: extensive. I had the clear impression that everybody that participated in the discussion were in favor of this library, albeit they did not have time to submit a full review. I did not hear a single statement saying that this library should be rejected. Thanks to everybody that participated in the review and its discussions. Issue Summary ------------- Below is given a list of topics that must be adressed before the library can be included into boost. In general, we should try to discuss them one at a time in seperate threads. Many people suggested various extensions, new algorithms (e.g. from adope), etc. **In general we should not require Neil to add all these if he does not have the time currently: the basic infrastructure, the concepts, the naming and organization of the library is much more important. Then we can add all these things later.** 1: documentaion =============== The documentation should clearly reflect if an algorithm delegates to a standard algorithm. If the algorithm is new, then it should state complety and exception-safety. More examples would be welcome. Sometimes the rationale and explanations could be improved, e.g for operator|(). 2: return type specification for find() etc =========================================== There where no major objection to the mechanism, but some found the syntax ugly. I believe the suggested syntax (e.g.) boost::find[_f,_e]( range, x ) boost::find[_f+1,_e]( range, x ) was considered good by most. 3: namespace organization ========================= Currently the library uses the namspaces boost boost::adaptors Some raised concern about putting the algorithms straight in the boost namespace before we have a general agreement on where to put algorithms (e.g. in boost::algorithm or boost::ranges or whatever). I think it will make sense to put each algorithm in its own header, since we might have to include additional standard library headers for calling algorithms that are implemented as member functions (but see 7 below). Feedback is most welcome. 4: naming convention for adaptors ================================= The following have been proposed throughout the review (here examplified with "transform"): | transformed( fun ) | transform( fun ) | transform_view( fun ) | view::transform( fun ) There where no consensus during the review. Other libraries seem to use the _view suffix, which is a strong argument for that candidate (in that case, I suggest to drop the adaptors namespace). 5: naming convention for the adaptor generators =============================================== Many people like to be able to say make_transform_range(r,fun) instead of r | transformed( fun ). There was no concensus on how to name these functions. Here are some candidates: make_transform_range( r, fun ) transformed( r, fun ) transform( r, fun ) (*) transform_view( r, fun ) (*) was dislike by some because it has exactly the same spelling as the algorithm transform. Many felt that the confusion is too big if view generators are not named different from the actual algorithms. 6: reintroducing _if variants of algorithms =========================================== An important problem with the suggested approach was the the iterator returned by an algorithm after applying | filtered( pref ) are now filtered iterators and so one needs to manually unwrap the return iterator. This provided enough justification for reintroducing these algorithms. (One could imagine that this unwrapping was done automatically by a conversion operator such that iterator i = boost::find( r | boost::filtered( pred ), x ); "just worked". However, the syntax is still slightly worse than just using the original algorithm). Generic programming is concerned with the use of orthogonal concepts which put together yields all possible combinations of algorithms. If we reintroduce all _if algorithms, we have to aks ourselves "when does it end?". Should all new algorithms then simply add _if variants? This seems very much against the spirit of generic programming. The problem with the iterators being changed (as in the find example) seems to suggest the following guideline: "If the algorithm returns an iterator, it makes sense to provide an _if overload. Otherwise it does not." Under this guideline, find_if() should be there, but count_if() should not be provided. 7: should algorithms call member function when possible? ======================================================== I heard one strong voice against this. The reason was that the algorithm implemented as member function often has quite different guarantees w.r.t. complexity, reference and iterator stabililty. I think this is a very strong argument. Also, we can add this later if good arguments appear, but it is much harder to take away. We also have to remember Scott Meyers item "Beware of container independent code" which also suggest that this is a bad idea. At the very menimum, the original algorithm and the member function should have similar semantics. This seems to suggest that we can call set::lower_bound() from boost::lower_bound(). In that case, the best way would probably be to add these as overloads in the boost namespace: template< class T, class A > typename std::set<T,A>::iterator lower_bound( std::set<T,A>& s ); template< class T, class A > typename std::set<T,A>::const_iterator lower_bound( const std::set<T,A>& s ); 8: making return values of algorithms consistent/intuitive ========================================================== For example, sort(r) returns the sorted range, but sort_heap(r) does not. Similar issues for partial_sort(). Please go through all algorithms to see if this done correctly. 9: output range concept? ========================= It appears that the only use for an output iterator in the library was for boost::copy(rng,iter), and the only use for that function was for "sinks" like std::ostream_iterator<T>(...). This seems to be the only safety hole left in the library. Here's an idea to how we might remove that: create a new "copy sink" concept: struct array_copy_sink { ... template< class Iterator > copy( Iterator begin, Iterator end ) { ... } }; Then we might imagine boost::copy( rng, boost::ostream_sink(std::cout) ); boost::copy( rng, boost::array_sink(an_array) ); boost::copy( rng, boost::ptr_sink(begin,end) ); boost::copy( rng, boost::front_insert_sink(a_deque) ); ... For optimal performance, we also need a "nonoverlapping copy sink" concept, and an algorithm that expects that sink (or that boost::copy() determines the type of the sink automatically). 10: automatic projection ======================= Adope has algorithms overloaded such that projection is very easy: struct my_type { int member; double another_member; }; //... my_type a[] = { { 1, 2.5 }, ... }; // sort the array by the first member: sort(a, less(), &my_type::member); my_type* i = lower_bound(a, 5, less(), &my_type::member); We should be able to express this well, albeit not as concise, with my_type* i = boost::lower_bound( a | project( &my_type::member ), 5, less() ); where project( ... ) could simply return a transform iterator constructed with boost::bind(). There is another problem, however, because now the return value is a tranform_iterator of some form. Appending .base() would solve it, albeit it is somewhat ugly. Again this might raise the question of an implicit conversion. I just want to say this is not a critical issue as we can always add these overloads. --- End of Issues ---- Again, I would like to thank everybody that participated in the review. best regards Thorsten, review manager

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[preprocessor] Nested FOR_EACHs
by Reimund Klemm 27 Apr '09

27 Apr '09

Hello, is it possible to nest FOR_EACH statements with the preprocessor? In my example it seems not to work: #include <boost/preprocessor/seq/for_each_i.hpp> #define DECLARE_TEST2(r,data,i,elem) \ 1; /**/ #define DECLARE_TEST(r,data,i,elem) \ BOOST_PP_SEQ_FOR_EACH_I(DECLARE_TEST2,data,data); /**/ #define SEQ ((1)(NACK_SN)(10)) ((1)(E1)(1)) ((1)(E2)(1)) int main(){ BOOST_PP_SEQ_FOR_EACH_I(DECLARE_TEST,SEQ,SEQ) return 0; } Thanks a lot for comments. Reimund

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[Spirit] leaf_node_d compile time error
by Chris Uzdavinis 26 Apr '09

26 Apr '09

Hi, I'm upgrading some code from boost 1.33 to 1.38, and upgrading compilers from gcc 4.1 to 4.3.3. Code that used to work is no longer compiling, and I'm running out of ideas what might be the problem. While the real code is significantly larger, I've managed to extract the problem down to this short example. #define BOOST_SPIRIT_USE_OLD_NAMESPACE #include "boost/spirit/include/classic_core.hpp" #include "boost/spirit/include/classic_ast.hpp" using namespace boost::spirit; struct Test_Parser : public grammar<Test_Parser> { template <typename ScannerT> struct definition { definition(Test_Parser const & /*self*/) { test_filter = leaf_node_d[ ch_p('=') ] //<<<<<<< HERE ; } rule<ScannerT> test_filter; rule<ScannerT> const & start() const { return test_filter; } }; }; int main() { using namespace boost::spirit; char const * str = "="; Test_Parser parser; parse_info<> info = parse(str, parser, space_p); } When I use leaf_node_d[], it doesn't compile. Removing leaf_node_d, and all is well. The error is ugly, but ultimately is this: error: no type named node_factory_t in class boost::spirit::leaf_node_parser<T>::parse(const ScannerT&) const I've spent a few hours trying to grok the code and am falling short. Any help would be appreciated. g++ -I $BOOST_ROOT foo.cpp /usr/local43/include/boost-1_38/boost/spirit/home/classic/tree/common.hpp: In member function typename boost::spirit::parser_result<boost::spirit::leaf_node_parser<T>, ScannerT>::type boost::spirit::leaf_node_parser<T>::parse(const ScannerT&) const [with ScannerT = boost::spirit::scanner<const char*, boost::spirit::scanner_policies<boost::spirit::skipper_iteration_policy<boost::spirit::iteration_policy>, boost::spirit::match_policy, boost::spirit::action_policy> >, T = boost::spirit::chlit<char>]: /usr/local43/include/boost-1_38/boost/spirit/home/classic/core/non_terminal/impl/rule.ipp:235: instantiated from typename boost::spirit::match_result<ScannerT, ContextResultT>::type boost::spirit::impl::concrete_parser<ParserT, ScannerT, AttrT>::do_parse_virtual(const ScannerT&) const [with ParserT = boost::spirit::leaf_node_parser<boost::spirit::chlit<char> >, ScannerT = boost::spirit::scanner<const char*, boost::spirit::scanner_policies<boost::spirit::skipper_iteration_policy<boost::spirit::iteration_policy>, boost::spirit::match_policy, boost::spirit::action_policy> >, AttrT = boost::spirit::nil_t] foo.cpp:28: instantiated from here /usr/local43/include/boost-1_38/boost/spirit/home/classic/tree/common.hpp:903: error: no type named node_factory_t in class boost::spirit::leaf_node_parser<T>::parse(const ScannerT&) const [with ScannerT = boost::spirit::scanner<const char*, boost::spirit::scanner_policies<boost::spirit::skipper_iteration_policy<boost::spirit::iteration_policy>, boost::spirit::match_policy, boost::spirit::action_policy> >, T = boost::spirit::chlit<char>]::result_t make: *** [.obj/foo.o] Error 1 -- Chris

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Boost Graph Library documentation unclear
by Lindley M French 26 Apr '09

26 Apr '09

I've been trying to use the Boost Graph Library. For the most part I'm working it out. However, I'm finding the documentation annoyingly decentralized....it isn't interlinked enough, at the very least. Too hard to go from "how do I use X" to "oh, here's the documentation on X." Took me half an hour just to find *something* on the add_edge function (turns out it's on the Concepts page?), and what's there *barely* qualifies as a prototype, much less a proper man page. My current question is regarding properties. Some of the algorithms specify the "edge_weight" property as if it's something all edges have, and the vertex_index property as if it's something all vecS-specified graphs have. Yet I can't find any documentation explicitly confirming this, and my compiler seems to disagree in any case. http://www.boost.org/doc/libs/1_38_0/libs/graph/doc/kruskal_min_spanning_tr… Can something be done about the state of the documentation, and is there a comprehensive list of default properties available somewhere (together with how those are replaced or supplemented when user properties are introduced)?

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initializing intrusive_ptrs through library calls
by Zachary Turner 26 Apr '09

26 Apr '09

I frequently use COM, and I've written an add_ref() and release() so that I can use my COM objects with boost::intrusive_ptr. However, one generally obtains these pointers through a library call that accepts a T** or a void**, and returns a pointer that's already been AddRef'd the first time. Normally it would go something like this: template<typename T> d3d_ptr<T> take_ptr(T* t) { return d3d_ptr<T>(t, false); } ID3DXFont* pFont = NULL; D3DXCreateFontIndirect(m_pDeviceObject, &fontDesc, &pFont); m_spFont = take_ptr(pFont); To remove these extra 2 lines I wrote the following class / function: template<typename T> class recv_by_addr_t { public: recv_by_addr_t(d3d_ptr<T>& r) : m_auto(r), m_raw(NULL) {} ~recv_by_addr_t() {m_auto = take_ptr(m_raw);} operator T**() { return &m_raw; } private: T* m_raw; d3d_ptr<T>& m_auto; }; template<typename T> recv_by_addr_t<T> recv_by_addr(d3d_ptr<T>& rptr) { return recv_by_addr_t<T>(rptr); } And I can now call the function like this: D3DXCreateFontIndirect(m_pDeviceObject, &fontDesc, recv_by_addr(m_spFont)); I feel like this is pretty solid, but figured I should ask the gurus :) Even in the case where the function errors out and sets the thing to NULL, the original pointer should still get correctly released. Anything wrong with this approach?

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Boost 1.39.0 beta 1 is available for download
by Beman Dawes 26 Apr '09

26 Apr '09

Boost 1.39.0 beta 1 is available for download from SourceForge. See http://sourceforge.net/project/showfiles.php?group_id=7586&package_id=8041&… New Libraries: Signals2. Updated Libraries: Asio, Flyweight, Foreach, Hash, Interprocess, Intrusive, Program.Options, Proto, PtrContainer, Range, Unordered, Xpressive. Updated Tools: Boostbook, Quickbook. Plus the usual bug fixes to numerous libraries. Please report any problems to the Boost users or developers mailing list. Thanks, --Beman Dawes, Daniel James, and all the other Boosters who help get releases out

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Examples....
by Campagne 26 Apr '09

26 Apr '09

Dear all I am a quite new in Boost... Although I have experienced successfuly the smart_ptr library. Now, I would like to use IOSTREAM library. Even if the tutorial and User Guide are fine, they describe mostly how-to-write-xyz but very rarely how-to-use in practice. For instance I despearate to see an exmple on how-to-use the "line_wrapping_input_filter" example... Does someone can 1) tell me if there is somewhere example of how-to-use for end-user IOSTREAM features? 2) if someone as used the example and how... Best. JE -- +++++++++++++++++++++++++++++++++++++++ Jean-Eric Campagne Laboratoire de l'Accélérateur Linéaire d'Orsay IN2P3/CNRS et Université Paris XI LAL Orsay - B.P 34 91898 Orsay Cedex Tél: 0164468429 from abroad +3316.. Fax: 0164468397 +++++++++++++++++++++++++++++++++++++++

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ASIO, boost::function in VC7.1
by Kimon Simons 26 Apr '09

26 Apr '09

Hi all, I started playing with ASIO timers and after scanning through the relevant docs, I set up a small case. Please find below the code snippet. The IntervalEvent class is supposed to fire the event provided on the construction at a frequency equal to the durationInterval. Somehow the code below fails to compile on VC7.1. I am getting several warnings and the error: c:\program files\boost\boost_1_38\boost\mem_fn.hpp(343) : error C4716: 'boost::_mfi::dm<void __thiscall IntervalEvent::(boost::system::error_code &),IntervalEvent>::operator()' : must return a value I have not tried yet gcc. Probably I am doing something stupid. Any ideas? Further to that, I am wondering, in principle should I cancel the deadline_timer on the destructor of the IntervalEvent class? Does the io_service class know when any of the deadline_timers that is being registered goes out of scope? Thank you very much in advance. Any help would be highly appreciated. Kimon #include <boost/function.hpp> #include <iostream> #include <boost/asio.hpp> #include <boost/thread.hpp> #include <boost/bind.hpp> #include <boost/date_time/posix_time/posix_time.hpp> class Counter { public: Counter():m_value(0) { } void onIncrement() { ++m_value; std::cout<<"Counter is "<<m_value<<std::endl; } protected: int m_value; }; class IntervalEvent { public: IntervalEvent(boost::asio::io_service &io, long durationSeconds, boost::function<void(void)> event): m_intervalDuration(durationSeconds), m_timer(io,boost::posix_time::seconds(m_intervalDuration)), m_event(event) { //io_service::run is running in only one thread m_timer.async_wait(boost::bind(&IntervalEvent::handler, this)); } ~IntervalEvent() { //should I call m_timer.cancel to notify the io_service? } void handler(boost::system::error_code& error) { if(error!= boost::asio::error::operation_aborted) { m_event(); reset(m_intervalDuration); } } void reset(long duration) { if (m_timer.expires_from_now(boost::posix_time::seconds(duration)) > 0) { m_intervalDuration = duration; //reset the async wait m_timer.async_wait(boost::bind(&IntervalEvent::handler, this)); } else { //Timer already canceled } } void cancel() { m_timer.cancel(); } size_t getCurrentInterval() const { return m_intervalDuration; } protected: long m_intervalDuration; boost::asio::deadline_timer m_timer; boost::function<void(void)> m_event; }; int main() { boost::asio::io_service io; boost::shared_ptr<boost::asio::io_service::work> work(new boost::asio::io_service::work(io)); boost::thread ioservice_thread(boost::bind(&boost::asio::io_service::run, &io)); std::vector<boost::shared_ptr<IntervalEvent> > events; Counter count; long duration = 1; boost::shared_ptr<IntervalEvent> firstEvent(new IntervalEvent(io, duration, boost::bind(&Counter::onIncrement,boost::ref(count) )) ); events.push_back(firstEvent); char response = 'N'; while(response == 'N') { std::cout<<"Create a new interval event? [Y/N]"<<std::endl; std::cin>>response; if(response == 'Y') { boost::shared_ptr<IntervalEvent> test(new IntervalEvent(io, duration, boost::bind(&Counter::onIncrement,boost::ref(count) )) ); events.push_back(test); } } //cancel interval events for(std::vector<boost::shared_ptr<IntervalEvent> >::iterator it = events.begin(), itEnd = events.end(); it!=itEnd; ++it) { (*it)->cancel(); } //reset ioservice_work work.reset(); ioservice_thread.join(); return 0; }

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